float oneshot_get_cm_range_sensor_gp2ya21y(const int iInfraPin)
{
  const float fScale = 5.0f/1024.0f;
  float fDistance = -1.0f;

  int iAnalogValue = analogRead(iInfraPin);
  float fVolts = iAnalogValue*fScale;
  if(fVolts>0.4 && fVolts<2.25)
  {
    fDistance = 32.0f*pow(fVolts, -1.10f);
  }

  // retour en cm
  return fDistance;
}
